Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.87	4.342%	$177.2458	$177.25	$177.25	$177.20
Purchase #2	$54.31	13.287%	$61.5262	$61.53	$61.55	$61.50
Purchase #3	$153.51	8.795%	$167.0112	$167.01	$167.00	$167.00
Purchase #4	$150.38	10.412%	$166.0376	$166.04	$166.05	$166.00
Purchase #5	$81.28	3.212%	$83.8907	$83.89	$83.90	$83.90
Purchase #6	$229.36	13.831%	$261.0828	$261.08	$261.10	$261.10
Purchase #7	$131.67	4.472%	$137.5583	$137.56	$137.55	$137.60
7 purchase totals =	$970.38		$1,054.3526	$1,054.36	$1,054.40	$1,054.30